This is a competing application for renewal of a post-doctoral training grant in molecular virology and oncology that is currently in year 25. Six slots per year are requested for individuals with the Ph.D., M.D., or M.D./Ph.D. degree. The principal goal of the program is to provide an intensive two-year laboratory research experience under the direct supervision of one of the participating faculty in order to prepare the trainees for a career in independent basic cancer research. Trainees are also expected to attend courses in cancer and biomedical ethics and to gain experience in presenting their work. Several new initiatives are planned or underway to help the trainees identify with this Cancer Research Training Program. The overall success of the Training Program can be measured by the long-standing ability of our former trainees in assuming independent positions in cancer-related research. The investigators comprising the faculty are drawn from numerous departments at Yale and share a common interest in using molecular genetic approaches to obtain a mechanistic molecular understanding of oncogenesis, with a particular emphasis on the interactions between tumor viruses and cells. A number of the faculty participate in a Program Project Grant on Viral Transformation that was recently renewed for a five-year period. In addition to their related individual research interests, the investigators are linked by numerous collaborative projects, frequent informal consultations, discussions, sharing of materials and participation in joint research seminars, journal clubs and teaching activities. To ensure the continued vitality and success of this training program, several outstanding new faculty have been recruited who share a research interest in the molecular mechanisms of carcinogenesis. These new trainers focus on aspects of cell cycle control, signal transduction, mutagenesis, and viral replication. The Program Director, Daniel DiMaio, M.D., Ph.D., Professor and Vice Chairman of Genetics, devotes his laboratory effort to the study of papillomaviruses and their effects on cell growth. He is also the Principal Investigator of the Program Project Grant, "Molecular Basis of Viral Transformation", the Director of the Molecular Virology Program of the Yale Comprehensive Cancer Center, and a member of the Executive Committee of the Center. In these capacities, he is well positioned to foster interactions among other members of the faculty in the School of Medicine.